It is generally known that when a knitted fabric is cut, its cut-end tends to be curled.
When such fabric workpieces are cut together and overlapped for sewing together, it is necessary to stretch the workpieces to flaten the curl before sewing the workpieces together.
FIG. 8 to FIG. 14 illustrate one conventional type of apparatus for eliminating curls described in Japanese patent publication No. 59-45395 titled "apparatus for eliminating curls", published on Nov. 6, 1984, and filed on June 9, 1981.
This apparatus includes a presser bar 101 and presser foot 102 attached to the presser bar 101. The apparatus also includes a base plate 103 fixed to a bed 104.
A first curl-eliminating body 105 is located at the front side of the presser foot 102. A slope 107, formed at the end of the first curl-eliminating body 105, is down-sloped rightwardly when viewed from an operator.
The tip end 108a of projection 108 is down-sloped rightwardly so that it creeps into the curled portion K of the workpiece (See FIG. 12). Arrow Y in FIG. 8 indicates the direction in which the workpiece is fed.
Another slope 109 is down-sloped towards the operator. A middle plate 110 is located under the first curl-eliminating body 105 and adapted to rotate around a shaft 106.
At the end of the middle plate 110, a projection 111 is provided. This projection 111 is larger than the projection 108 as shown in FIG. 9, and provides a slope 112 and another slope 113.
The first curl-eliminating body 105 and the middle plate 110 contact one another only at projection 108 and projection 111.
Springs 118 and 119 urge the first curl-eliminating body 105 and the middle plate 110 to rotate counter clockwise when viewed from the operator side such that the middle plate 110 is clamped between the first curl-eliminating body 105 and the base plate 103.
The base plate 103 provides a second curl-eliminating body 114 at its end. An L-shaped arm 120 is rotatably supported by a support column 120A as shown in FIG. 9, FIG. 10, and FIG. 11, and its end 120a contacts the surface of the first curl-eliminating body 105 as shown in FIG. 10. Another end 120b of the L-shaped arm 120 engages horizontal bar 101a which extends from the presser bar 101.
A restricting plate 121 is located between the presser foot 102 and the second curl-eliminating body 114. The restricting plate 121 contacts the edge of the workpiece W and guides the workpiece W as shown in FIG. 12.
Referring to FIG. 10, the operation of this conventional curl eliminator will be explained hereafter.
When the presser bar 101 is lifted by knee-operation, the presser foot 102 and the horizontal bar 101a will also be lifted, and as a result, L-shaped arm 120 rotates clockwise such that end 120a presses the first curl-eliminating body 105 downwardly, so that the first curl-eliminating body 105 rotates in a clockwise direction. The presser foot 102 than descends for sewing, and the horizontal bar 101a also descends. As a result, the L-shaped arm 120 rotates counter clockwise, and is released from pressing the first curl-eliminating body 105. Thereby, springs 118 and 119 urge the first curl-eliminating body 105 and the middle plate 110 to rotate counter clockwise such that two cloths W.sub.1, and W.sub.2, which constitute the workpiece W, are clamped between the middle plate 110 and the first and second curl eliminating bodies, respectively.
At this point, the sewing machine starts and the workpiece W is fed in the direction of arrow Y.
Since the operational action for both upper cloth W.sub.1 of workpiece W and lower cloth W.sub.2 of workpiece W are virtually the same, reference will be made to only the upper cloth W.sub.1.
As the workpiece W is fed, the curl K.sub.1 approaches projection 108 of the first curl-eliminating body 105, and the curl K.sub.1 is smoothly introduced into the projection 108 since a slope 108T is formed in the same direction as the curling K.sub.1 as shown in FIG. 13.
Since the projection 108 is situated in front of slope 107, the curl K.sub.1 will be pushed rightward and stretched as the workpiece W is fed so that the curled portion diminishes.
Referring to FIG. 13, the upper cloth W.sub.1 of the workpiece W is clamped between the tip end of the projection 108 and the middle plate 110. Since the contact between projection 108 and the middle plate 110 is one-point contact, when the workpiece W is pulled by the dog feed (not shown), the curl K.sub.1 tends to be diminished.
As the cloth W.sub.1 is further fed and passes over the slope 107, the curl K.sub.1 becomes smaller as shown in FIG. 14.
Finally, the curl K.sub.1 creeps in between the first curl-eliminating body 105 and the middle plate 110, and is flattened. The flattened curl K.sub.1 is further fed to the presser foot 102 and is sewed by a needle N (FIG. 12).
The conventional type of eliminator just described is available, where the curls K.sub.1 and K.sub.2 are curled outwardly as shown in FIG. 6 as curls 15 and -6. Where, however, the curls K.sub.1, and K.sub.2 are curled inwardly as shown in FIG. 7 as curls 17 and 18, the conventional type of eliminator is not available. If some other curl stretching devices are provided at the middle plate 110, the structure of the conventional eliminator becomes more complicated and invites higher costs.